1. Field of the Invention
This invention relates generally to rapidly solidified nickel-rich alloys obtained by adding small amounts of boron. This invention also relates to the preparation of these materials in the form of rapidly solidified powder and consolidation of these powders (or alternatively, the rapidly solidified ribbon-like material) into bulk parts which are suitably heat treated to have desirable properties. This invention also relates to the preferred nickel-rich metal alloy compositions made by this method.
2. Description of the Prior Art
Rapid solidification processing (RSP) techniques offer outstanding prospects of new cost effective engineering materials with superior properties [See Proc. Int. Conf. on Rapid Solidification Processing; Reston, Va., 1980; Published by Claitors Publishing Division, Baton Rouge, La. ]Metallic glasses, microcrystalline alloys, supersaturated solid solutions and ultra-fine grained alloys with highly refined microstructures, in each case often having complete chemical homogenity, are some of the products that can be made by utilizing RSP. (See Rapidly Quenched Metals, 3rd, Int. Conf. Vol. 1 and 2, Cantor Ed; the Metals Society, London, 1978).
Several techniques are well established in the state of the art to economically fabricate rapidly solidified alloys (at cooling rates of .about.10.sup.5 to 10.sup.7 .degree.C./sec) as ribbons, filaments, wire, flakes or powders in large quantities. One well known example is melt spin chill casting whereby the metal is spread as a thin layer on a conductive metallic substrate moving at high speed to form rapidly solidified ribbon (see Proc. Int. Conf. on Rapid Solidification Processing, Reston, Va., Nov. 1977).
The current technological interest in materials produced by RSP, especially when followed by consolidation into bulk parts may be traced in part to the problems associated with micro and macro segregation and undesirable massive grain boundary eutectic phases that occur in highly alloyed materials during conventional slow cooling processes i.e. ingot or mold casting. RSP removes macrosegregation altogether and significantly reduces spacing over which micro-segregation occurs, if it occurs at all.
The design of alloys made by conventional slow cooling processes is largely influenced by the corresponding equilibrium phase diagrams which indicate the existence and co-existence of the phases present in thermodynamic equilibrium. Alloys prepared by such processes are in or at least near equilibrium. The advent of rapid quenching from the melt has enabled material scientists to stray further from the state of equilibrium and has greatly widened the range of new alloys with unique structures and properties available for technological applications.
Many nickel base alloys are used for chemical and marine parts where corrosion resistance and white color are important.
Nickel base alloys containing essentially about 30 wt% cooper which are commercially known as Monel are widely used in a variety of applications. The alloy may be cast, rolled or forged and can be annealed after cold working. It is resistant to corrosion and to the action of many acids and will retain its bright nickel white surface under ordinary conditions. (See Materials Handbook, George S. Brady and Henry R. Clauser, p. 499, Published by McGraw-Hill Book Co., 1977).
There have been limited efforts as reported in the prior art involving the use of rapid solidification processing techniques to synthesize new and improved nickel base alloys. A need therefore exists to develop new nickel base alloys with unique chemical compositions and structures exhibiting superior mechanical properties, and corrosion and/or oxidation resistance for numerous industrial applications.